[QuadList] Scanning Documents - was: Slow Motion Quad

[Don Norwood]

----- Original Message ----- From: Ted Langdell
  Don Norwood might have some suggestions on method and image sizes/pixels per inch, etc.


  Ted


Hi Ted :

I've tried lots of different scanning methods over the years, trying to find a good balance between file size and image quality.  Hardware and software have both improved so much that it's far easier than it used to be.  In fact, I need to re-scan many of the brochures on the website to bring them up to current standards.  My goal is for all future scans to include searchable text within the PDF, but none of the documents I have on-line currently have that capability.

In general, I usually start with a 300 DPI scan which is OK for text and most pictures, but higher resolution may be appropriate depending on the quality of the original.  These are stored as either jpeg's with minimal compression or as bitmaps where higher quality is desired.  This gives me a hi-res image (but large size) file from which to generate the desired format.  Then if I need a jpeg intended for screen viewing, I'll reduce the original to 96 dpi, resize if needed to fit the screen, and use a good bit of compression to further reduce the file size.  The exact amount of compression is often determined by experimentation to see what looks acceptable.  I think you'll find that with most software, starting with a hi-res scan and then generating a lower res compressed file will give a much better result than just doing a low-res scan to begin with.  Be aware however, that some scanner software will do this automatically depending on what options are selected, such as moire filtering or descreening.

Most of my scans end up as pdf files, but again, the exact "formula" for producing them depends on the intended use.  The ones that I have on the web site are usually not intended for printing, and so they are down-sampled to generate a smaller file that still looks OK on a computer screen.  These are also image files that do not have searchable text.  By converting to searchable text, only the non-text portions of the scan will be stored as images, and so the overall file size can be greatly reduced.

Bottom line is that just like with modern video gear, there are so many different "tricks" and possibilities with digital processing that you just need to be familiar with your software.  A scan can be as quick and easy as a mouse click, or as involved as you care to make it.  Correction of color, gama, brightness, contrast, geometric alignment, descreening, detail enhancement etc etc etc can be fully automatic or can take lots of time if you want to do it yourself.  

Don Norwood
Digitrak Communications, Inc.
www.digitrakcom.com

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